Operating Mode Distinguishing Method, Touch Point Locating Method and Touch Control Circuit

ABSTRACT

An operating mode distinguishing method, a touch point determining method and a touch control circuit are provided. It is determined whether an underwater mode is entered according to a self capacitance value and a mutual capacitance value. In the underwater mode, a touch point position is determined according to deformation of a substrate.

This application claims the benefit of Taiwan application Serial No.104110706, filed Apr. 1, 2015, the subject matter of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to an operating mode distinguishingmethod, a touch point locating method and a touch control circuit, andmore particularly to an operating mode distinguishing method, a touchpoint locating method and a touch control circuit applied for underwateroperations.

2. Description of the Related Art

As smart phones and tablet computers have become mainstream informationproducts, touchpads that perform command input using touch controlgestures have also become popular human-machine interface (HMI) controlapparatuses among users.

FIG. 1a shows a sectional view of a conventional capacitive touchpad. Asshown, a plurality of sensing electrodes 11 to 14 are disposed below asubstrate 1, which is a cover lens made of glass, for example. When afinger 19 touches the top of the substrate 1, some of the sensingelectrodes 11 to 14 are coupled to the finger 19 to generate changes incapacitance values. For example, a self capacitance CS3 of selfcapacitances CS1 to CS4 in the diagram has a change in the capacitancevalue due to the touch of the finger 19. The sensing electrodes 11 to 14are then scanned by a touch control circuit (not shown) to detectchanges in mutual capacitances CM1 to CM3 among the sensing electrodes11 to 14 and/or the above self capacitances CS1 to SC4, hence furtherestimating the position of the finger 19.

The number of portable devices with a waterproof function is increasing.However, when a portable device including the abovementioned capacitivetouchpad is operated under water, water 18 covering the top of thesubstrate 1 (as shown in FIG. 1b ) may cause an effect similar to anentire hand pressing upon the capacitive touchpad, leading to an issueof incapable of effectively determining the touch position. Therefore,there is a need for a capacitive touchpad that is operable under water.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide an operatingmode distinguishing method applied to a capacitive touch apparatus. Theoperating mode distinguishing method includes: obtaining a selfcapacitance value and a mutual capacitance value in the capacitive touchapparatus; entering a first operating mode when a change in the selfcapacitance value does not exceed a first threshold and a rising rangeof the mutual capacitance value is greater than a second threshold; andentering a second operating mode when the rising range of the mutualcapacitance value is not greater than the second threshold.

According to an embodiment of the present invention, the operating modedistinguishing method further includes: entering the second operatingmode when the change in the self capacitance value exceeds the firstthreshold.

According to an embodiment of the present invention, the first operatingmode is an underwater mode, and the second operating mode is a normalmode.

It is another object of the present invention to provide a touch pointlocating method applied to a capacitive touch apparatus. The capacitivetouch apparatus includes a plurality of sensing electrodes and a commonelectrode. The touch point locating method includes: providing a touchsensing signal to the sensing electrodes when the capacitive touchapparatus operates in a normal mode, and providing the touch sensingsignal to the common electrode when the capacitive touch apparatusoperates in an underwater mode; detecting a plurality of capacitancevalues from the sensing electrodes in response to the touch sensingsignal, respectively; and determining a position of a touch pointaccording to the capacitance values.

According to an embodiment of the present invention, the touch pointlocating method further includes: providing a fixed voltage to thesensing electrodes when the capacitive touch apparatus operates in theunderwater mode and the touch sensing signal is inputted to the commonelectrode.

According to an embodiment of the present invention, when the capacitivetouch apparatus operates in the underwater mode, the capacitance valuesare capacitance values between the sensing electrodes and the commonelectrode.

According to an embodiment of the present invention, the touch pointlocating method further includes: correcting the position of the touchpoint by a position correcting correspondence table.

According to an embodiment of the present invention, the capacitivetouch apparatus further includes a substrate. The sensing electrodes aredisposed on the substrate. The touch point causes deformation of thesubstrate to change a distance between the common electrode and at leastone sensing electrode of the sensing electrodes.

According to an embodiment of the present invention, the capacitivetouch apparatus further includes a substrate. The sensing electrodes aredisposed on the substrate. The capacitance values are associated withdeformation of the substrate caused by the touch point.

It is another object of the present invention to provide a touch controlcircuit for controlling a capacitive touchpad. The capacitive touchpadincludes a plurality of sensing electrodes and a common electrode. Thetouch control circuit includes: a capacitance sensing unit, whenoperating in a normal mode, outputting a touch sensing signal to thesensing electrodes and detecting a plurality of capacitance values fromthe sensing electrodes to accordingly generate a sensing result, whenoperating in an underwater mode, outputting the touch sensing signal tothe common electrode, and detecting the plurality of capacitance valuesfrom the sensing electrodes to accordingly generate the sensing result;and a calculating unit, calculating a position of a touch pointaccording to the sensing result.

According to an embodiment of the present invention, when operating inthe underwater mode, the capacitance sensing unit detects a plurality ofcapacitance values between the sensing electrodes and the commonelectrode from the sensing electrodes.

According to an embodiment of the present invention, the capacitivetouchpad further includes a substrate. The sensing electrodes aredisposed on the substrate. When the touch control circuit operates inthe underwater mode, the capacitance values are associated withdeformation of the substrate caused by the touch point.

According to an embodiment of the present invention, when the touchcontrol circuit operates in the underwater mode, the capacitance sensingunit further outputs a fixed voltage to the common electrode.

It is yet another object of the present invention to provide a touchcontrol circuit for controlling an operating mode of a capacitive touchapparatus. The capacitive touch apparatus includes a plurality ofsensing electrodes. The touch control circuit includes: a capacitancesensing unit, detecting a self capacitance value and a mutualcapacitance value from the sensing electrodes; and an operating modedistinguishing unit, determining an operating mode of the capacitivetouch apparatus according to the self capacitance value and the mutualcapacitance value. When a change in the self capacitance value does notexceed a first threshold and a rising range of the mutual capacitancevalue is greater than a second threshold, the operating modedistinguishing unit determines that the capacitive touch apparatusoperates in a first operating mode. When the rising range of the mutualcapacitance value is not greater than the second threshold, theoperating mode distinguishing unit determines that the capacitive touchapparatus operates in a second operating mode.

According to an embodiment of the present invention, when the change inthe self capacitance value exceeds the first threshold, the operatingmode distinguishing unit determines that the capacitive touch apparatusoperates in the second operating mode.

According to an embodiment of the present invention, the first operatingmode is an underwater mode, and the second operating mode is a normalmode.

The above and other aspects of the invention will become betterunderstood with regard to the following detailed description of thepreferred but non-limiting embodiments. The following description ismade with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a and FIG. 1b are sectional views of a conventional capacitivetouchpad;

FIG. 2 is a block diagram of a capacitive touch apparatus of the presentinvention developed for improving drawbacks of the prior art;

FIG. 3a and FIG. 3b are schematic diagrams of using the apparatus inFIG. 2 to perform technical means for scanning a touch position;

FIG. 4 is a block diagram of a capacitive touchpad according to a secondpreferred embodiment of the present invention developed for improvingdrawbacks of the prior art;

FIG. 5a and FIG. 5b are schematic diagrams of differences in deformationat a border region and a central region of a substrate;

FIG. 5c is a schematic diagram of a position correcting correspondencegraph of the present invention;

FIG. 6 is a flowchart of an operating mode distinguishing method of thepresent invention; and

FIG. 7 is a schematic diagram of a capacitive touch apparatus accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Characteristics and advantages of the present invention are given indetail in the description of some typical embodiments below. It shouldbe noted that, various modifications made to the embodiments are to beencompassed within the scope of the present invention. Further, thedescription and drawings of the application are substantially forillustration purposes, and are not to be construed as limitations to thepresent invention.

FIG. 2 shows a schematic diagram of a capacitive touch apparatusdeveloped improving drawbacks of the prior art. As shown in FIG. 2, thecapacitive touch apparatus includes a capacitive touchpad 20 and a touchcontrol circuit 27. The capacitive touchpad 20 includes a substrate 2, aplurality of sensing electrodes 21 to 24, and a common electrode 25. Inpractice, the common electrode 25 may be additionally disposed for anexclusive use of the present invention, or may be selected fromelectrodes that are formed by an existing conductive plate in anelectronic apparatus provided with such capacitive touchpad and sharedwith other circuits. For example, when the capacitive touchpad isdisposed on a liquid crystal display (LCD) panel, the common electrode25 may be an electrode that controls the rotation of liquid crystals.

FIG. 3a shows a schematic diagram of a capacitive touch apparatus of thepresent invention operating in a normal mode. When the capacitive touchapparatus operates in the normal mode, e.g., when the capacitive touchapparatus operates normally in the air, the touch control circuit 27outputs a touch sensing signal (exemplified by a square wave in FIG. 3a) to the sensing electrodes 21 to 24. When a finger 29 is placed on topof the substrate 2, some electrodes of the sensing electrodes 21 to 24are caused to be coupled to the finger 29 to generate changes incapacitance values. By using the touch sensing signal to detect thesensing electrodes 21 to 24, the touch control circuit 27 can detect thechanges in the mutual capacitances CM1 to CM3 among the sensingelectrodes 21 to 24 and the self capacitances SC1 to SC4 of the sensingelectrodes 21 to 24 to further estimate the position of the finger 29.When the capacitive touch apparatus operates in the normal mode, thetouch control circuit 27 further may provide a fixed voltage to thecommon electrode 25. For example, the fixed voltage is a ground voltageto prevent the common electrode 25 from affecting touch sensingoperations.

FIG. 3b shows a schematic diagram of a capacitive touch apparatus of thepresent invention operating in an underwater mode. When the capacitivetouch apparatus operates in water, the capacitive touch apparatusswitches to operate in the underwater mode. At this point, the touchcontrol circuit 27 outputs the touch sensing signal to the commonelectrode 25, and provides a fixed voltage to the sensing electrodes 21to 24. By providing the common electrode 25 and providing the touchsensing signal to the common electrode 25, sensing capacitances CSC1 toCSC4 are respectively formed between the common electrode 25 and thesensing electrodes 21 to 24. When the capacitive touch apparatusoperates in the water as shown in FIG. 3b , deformation of the substrate2 is generated as the user finger 29 presses on the substrate 2, suchthat a distance between the common electrode 25 and one of the sensingelectrodes 21 to 24 is changed from a predetermined distance d to besmaller than the predetermined distance d, meaning that one of thesensing capacitances CSC1 to CSC4 corresponding to the pressed positionbecomes different (increased in this example) from the remainingcapacitance values. As such, the touch control circuit 27 may detect thecapacitance values of the sensing capacitance CSC1 to CSC4 between thesensing electrodes 21 to 24 and the common electrode 25 from the sensingelectrodes 21 to 24 to accordingly determine the position that ispressed by the finger 29. In practice, apart from adopting a commonmaterial such as glass to manufacture the substrate 2, to emphasize thedeformation of the substrate 2, a material having a larger flexibility,e.g., poly(methyl methacrylate), commonly referred to as acrylic. Air oranother flexible dielectric material layer or a dielectric adhesive (notshown) may be filled between the substrate 2 and the common electrode25. Operation details of the touch control circuit 27 and the method fordetermining whether operations are performed in the water or air are tobe give shortly.

FIG. 4 shows a block diagram of a capacitive touchpad according to asecond preferred embodiment of the present invention developed forimproving drawbacks of the prior art. As seen from FIG. 4, in thisembodiment, a plurality of sensing electrodes 41 to 44 are disposed on asurface of another carrier substrate 5 instead of on a surface of asubstrate 4. When water (not shown) covers on top of the substrate 4 ina way that a touch position cannot be determined by a conventionalscanning method, a touch control circuit 47 is capable of determiningthe underwater mode. Further, the present invention is capable ofdetecting the deformation of the substrate 4 caused by a user finger 49pressing on the substrate 4. In this embodiment, relative positions ofthe sensing electrodes 41 to 44 are not changed. However, due to thedeformation caused by the user finger 49 pressing on the substrate 4,the part that is pressed in the substrate 4 becomes closer to twoadjacent sensing electrodes of the sensing electrodes 41 to 44. Thus, achange in the distribution of the dielectric material among the sensingelectrodes 41 to 44 is caused, incurring differences among the mutualcapacitances CM1 to CM3 among the sensing electrodes 41 to 44. In thisembodiment, when the substrate 4 is glass, the dielectric coefficient ofglass is approximate four times of that of the air. When the substrate 4gets close to the sensing electrodes 41 to 44 due to the pressing finger49, the mutual capacitance values corresponding to the sensingelectrodes 41 to 44 are increased, with one pair of sensing electrodesamong the sensing electrodes 41 to 44 closest to the position of thesubstrate 4 pressed by the finger 49 having the largest change in themutual capacitance value. Thus, in this embodiment, by scanning theplurality of sensing electrodes 41 to 44 by the touch control circuit 47to detect the mutual capacitance values CM1 to CM3 among the sensingelectrodes 41 to 44, and locating the position corresponding to theincreased capacitance value, the position of the finger 49 can beestimated.

In the above embodiments, the change in the capacitance value is causedby the deformation of a curved substrate. However, as shown in FIG. 5aand FIG. 5b , even if the force applied by the finger is the same, thelevels of deformation at different positions, e.g., at a border regionand a central region of the substrate 2, may also be different. As such,the largest change in the capacitance values detected may notnecessarily be the correct position of the touch point pressed by thefinger, and a determination error may be resulted. Therefore, whendetermining the position of the touch point, a position correctingcorrespondence table may be used to perform a corresponding correctionas shown in FIG. 5c . The detected touch point is correspondinglyshifted to a correct position according to shift vectors (arrows shownin FIG. 5c ) corresponding to different positions to provide a moreaccurate determination for the touch point position. In practice, touchexperiments may be performed for various positions on the capacitivetouchpad, and the position correcting correspondence table is thengenerated according to the relationship between the actual touchposition and the detected touch position.

Further, to correctly distinguish whether the capacitive touch apparatusis operating in water, the touch control circuit 27 of the presentinvention may perform the method as shown by the flowchart in FIG. 6.FIG. 7 shows a schematic diagram of a capacitive touch apparatusaccording to an embodiment of the present invention. As shown, thecapacitive touch apparatus includes a capacitive touchpad 71 and a touchcontrol circuit 27. The touch control circuit 27 includes a capacitancesensing unit 72 and a processor 73. In this embodiment, the capacitivetouchpad 71 is illustrated by the capacitive touchpad in FIG. 2 to FIG.3b . In step 61, the capacitance sensing unit 72 detects at least oneself capacitance value and at least one mutual capacitance value fromthe sensing electrodes 21 to 24 of the capacitive touchpad 71. TheApplicant has discovered through experiments that, as shown in theoccurrence table in Table-1, for both the embodiment in FIG. 2 (commonlyreferred to as an out-cell touch panel) and the embodiment in FIG. 4(commonly referred to as an on-cell touch panel), after the capacitivetouch apparatus is placed in water, a noticeable rising trend of themutual capacitance value is measured, whereas the self capacitance valueis kept unchanged. It is deduced that, the mutual capacitance valuesbetween the adjacent electrodes placed in water are affected by waterhaving a high dielectric coefficient to lead to changes, hence causingthe overall mutual capacitance value to rise, with however the selfcapacitance value kept unchanged. In practice, the touch control circuit27 may compare the mutual capacitance values that the sensing electrodes21 to 24 detect at a preceding time point and a subsequent time point todetermine the change trend of the mutual capacitance. Similarly, thetouch control circuit 27 may also determine the self capacitance valuesthat the sensing electrodes 21 to 24 detect at a preceding time pointand a subsequent time point to determine the change trend of the selfcapacitance.

In step 62, the processor 73 determines the self capacitance value andthe mutual capacitance value detected by the capacitance sensing unit 72to distinguish the operating mode of the capacitive touch apparatus.When the change in the self mutual capacitance value does not exceed afirst threshold and a rising range of the mutual capacitance value isgreater than a second threshold, the processor 73 determines that thecapacitive touch apparatus is placed in water, and determines to causethe capacitive touch apparatus to operate in an underwater mode (step63). When the change in the self capacitance value exceeds the firstthreshold or the rising range of the mutual capacitance value is smallerthan the second threshold, the processor 73 determines that thecapacitive touch apparatus is not placed in water, and determines tocause the capacitive touch apparatus to operate in a normal mode (step64). The touch control circuit performs a determination operation at apredetermined time interval, e.g., once every half second, to determinewhether the operating environment is changed.

TABLE 1 Pressed and operated by a In water but In water and Type offinger under not pressed pressed by capacitance normal state by fingerfinger out-cell CM dropping Having rising Having rising touchcapacitance trend but trend but panel value cannot be cannot bepositioned positioned CS rising unchanged Having rising capacitancetrend but value cannot be positioned CSC unchanged unchanged Havingrising capacitance trend and can value be used for positioning on-cellCM dropping Having rising Having rising touch capacitance trend buttrend and can panel value cannot be be used for positioned positioningCS rising unchanged Having rising capacitance trend but value cannot bepositioned

Again referring to FIG. 7, when the capacitive touch apparatus operatesin the normal mode, the capacitance sensing unit 72 provides a fixedvoltage to the common electrode 25 in the capacitive touchpad 71, andoutputs a touch sensing signal to the sensing electrodes 21 to 24 in thecapacitive touchpad 71. Accordingly, the capacitance values of themutual capacitances CM1 to CM3 and/or self capacitances CS1 to SC4 aredetected from the sensing electrodes 21 to 24, and a sensing result isoutputted to the processor 73. The processor 73 then calculates theposition of the touch point according to the sensing result generated bythe capacitance sensing unit 72. When the capacitive touch apparatusoperates in the underwater mode, the capacitance sensing unit 72 changesto provide the fixed voltage to the sensing electrodes 21 to 24, andoutputs the touch sensing signal to the common electrode 25.Accordingly, the capacitance values of the sensing capacitances CSC1 toCSC4 between the common electrode 25 and the sensing electrodes 21 to 24can be detected, and a sensing result is outputted to the processor 73.The processor 73 then calculates the position of the touch pointaccording to the sensing result generated by the capacitance sensingunit 72.

In conclusion, the apparatus and method of the present invention arecapable of solving the drawback of the incapability of performing touchdetection under water of a conventional capacitive touchpad, and maythus be extensively applied to underwater cameras or touchpads and keysof waterproof smart phones.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited thereto. On the contrary, it is intended to cover variousmodifications and similar arrangements and procedures, and the scope ofthe appended claims therefore should be accorded the broadestinterpretation so as to encompass all such modifications and similararrangements and procedures.

What is claimed is:
 1. An operating mode distinguishing method, appliedto a capacitive touch apparatus, comprising: obtaining a selfcapacitance value and a mutual capacitance value in the capacitive touchapparatus; entering a first operating mode when a change in the selfcapacitance value does not exceed a first threshold and a rising rangeof the mutual capacitance value is greater than a second threshold; andentering a second operating mode when the rising range of the mutualcapacitance value is not greater than the second threshold.
 2. Theoperating mode distinguishing method according to claim 1, furthercomprising: entering the second operating mode when the change in theself capacitance value exceeds the first threshold.
 3. The operatingmode distinguishing method according to claim 1, wherein the firstoperating mode is an underwater mode, and the second operating mode is anormal mode.
 4. A touch point locating method, applied to a capacitivetouch apparatus comprising a plurality of sensing electrodes and acommon electrode, comprising: providing a touch sensing signal to thesensing electrodes when the capacitive touch apparatus operates in anormal mode, and providing the touch sensing signal to the commonelectrode when the capacitive touch apparatus operates in an underwatermode; detecting a plurality of capacitance values from the sensingelectrodes in response to the touch sensing signal; and determining aposition of a touch point according to the capacitance values.
 5. Thetouch point locating method according to claim 4, further comprising:providing a fixed voltage to the sensing electrodes when the capacitivetouch apparatus operates in the underwater mode and the touch sensingsignal is inputted to the common electrode.
 6. The touch point locatingmethod according to claim 4, wherein the capacitance values arecapacitance values between the sensing electrodes and the commonelectrode when the capacitive touch apparatus operates in the underwatermode.
 7. The touch point locating method according to claim 4, furthercomprising: correcting the position of the touch point by using aposition correcting correspondence table.
 8. The touch point locatingmethod according to claim 4, wherein the capacitive touch apparatusfurther comprises a substrate, the sensing electrodes are disposed onthe substrate, and a distance between the common electrode and at leastone sensing electrode of the sensing electrodes is changed bydeformation of the substrate caused by the touch point.
 9. The touchpoint locating method according to claim 4, wherein the capacitive touchapparatus further comprises a substrate, the sensing electrodes aredisposed on the substrate, and the capacitance values are associatedwith deformation of the substrate caused by the touch point.
 10. A touchcontrol circuit, adapted to control a capacitive touchpad comprising aplurality of sensing electrodes and a common electrode, the touchcontrol circuit comprising: a capacitance sensing unit, when operatingin a normal mode, outputting a touch sensing signal to the sensingelectrodes and detecting a plurality of capacitance values from thesensing electrodes to accordingly output a sensing result; whenoperating in an underwater mode, outputting the touch sensing signal tothe common electrode, and detecting the plurality of capacitance valuesfrom the sensing electrodes to accordingly generate the sensing result;and a calculating unit, calculating a position of a touch pointaccording to the sensing result.
 11. The touch control circuit accordingto claim 10, wherein when operating in the underwater mode, thecapacitance sensing unit detects a plurality of capacitance valuesbetween the sensing electrodes and the common electrode from the sensingelectrodes.
 12. The touch control circuit according to claim 11, whereinthe capacitive touchpad further comprises a substrate, the sensingelectrodes are disposed on the substrate, and the capacitance values areassociated with deformation of the substrate caused by the touch pointwhen the touch control circuit operates in the underwater mode.
 13. Thetouch control circuit according to claim 10, wherein when the touchcontrol circuit operates in the normal mode, the capacitance sensingunit further outputs a fixed voltage to the common electrode.
 14. Atouch control circuit, adapted to control an operating mode of acapacitive touch apparatus comprising a plurality of sensing electrodes,the touch control circuit comprising: a capacitance sensing unit,detecting a self capacitance value and a mutual capacitance value fromthe sensing electrodes; and an operating mode distinguishing unit,determining an operating mode of the capacitive touch apparatusaccording to the self capacitance value and the mutual capacitancevalue; wherein, when a change in the self capacitance value does notexceed a first threshold and a rising range of the mutual capacitancevalue is greater than a second threshold, the operating modedistinguishing unit determines that the capacitive touch apparatusoperates in a first operating mode; when the rising range of the mutualcapacitance value is not greater than the second threshold, theoperating mode distinguishing unit determines that the capacitive touchapparatus operates in a second operating mode.
 15. The touch controlcircuit according to claim 14, wherein when the change in the selfcapacitance value exceeds the first threshold, the operating modedistinguishing unit determines that the capacitive touch apparatusoperates in the second operating mode.
 16. The touch control circuitaccording to claim 14, wherein the first operating mode is an underwatermode and the second operating mode is a normal mode.